The present invention generally relates to electrochemical cells, i.e., batteries, and more particularly to a sealed closure assembly for sealing closed the open end of an alkaline battery container.
Conventional alkaline electrochemical cells generally include a steel cylindrical can having a positive electrode, referred to as the cathode, which comprises manganese dioxide as the active material. The electrochemical cell also includes a negative electrode, referred to as the anode, which comprises zinc powder as the active material. In a bobbin-type cell construction, the cathode is typically formed against the interior surface of the sealed can, while the anode is generally centrally disposed in the can. Alternately, in jelly-roll cells, the anode and cathode are spirally wound. A separator is located between the anode and the cathode, and an alkaline electrolyte solution, typically comprising potassium hydroxide (KOH), simultaneously contacts the anode, the cathode, and the separator. A conductive current collector is commonly inserted into the anode active material, and a seal assembly, which includes a seal member, provides closure to the open end of the steel can to seal the active electrochemical materials in the sealed volume of the can.
Cylindrical alkaline cells are commonly closed by inserting a preassembled collector and seal assembly in the open end of the steel can such that the assembly is disposed in the interior of the steel can. The collector and seal assembly typically includes the collector nail, an annular nylon seal, and an inner metal cover radially supporting the nylon seal. The steel can typically has a taper or an inwardly extending bead at its open end which serves to support the collector and seal assembly in the desired orientation prior to securing it in place. After the collector and seal assembly has been inserted in the can, an outer metal cover is placed over the assembly and the assembly and cover are secured in place by radially squeezing the can against the collector and seal assembly and outer cover, and crimping the edge of the can over the peripheral edge of the collector and seal assembly and outer cover to secure the outer cover and collector and seal assembly within the open end of the steel can.
A sealant, such as asphalt, is sometimes applied at the can and seal interface to further prevent alkaline electrolyte solution from leaking through the crimped closure. The sealant serves the purpose of preventing leakage, while the crimped closure provides the structural mechanical strength to the can closure. The sealant is generally required to be chemically resistant to the battery internal ingredients, including alkaline electrolyte which typically comprises potassium hydroxide. With the conventional crimped closure techniques, the seal assembly consumes considerable volume inside of the can and limits the height available for the active electrochemical materials including the positive and negative electrodes.
Accordingly, it is desirable to provide for a non-crimped sealed closure to the open end of the container that offers a strong mechanical closure for an alkaline electrochemical cell. In addition, it is desirable to provide for a sealed closure that allows for extended height electrodes.